1. Field of the Invention
The present invention relates to a positive-type photosensitive resin composition which is useful for use as a microfine processing resist in the fabrication of printed-wiring boards, integrated circuits, and the like, as well as for use as a photosensitive material in the manufacture of lithographic plates.
2. Description of the Prior Art
Hitherto, positive-type photosensitive resin compositions have been widely used in manufacturing integrated circuits, printed wiring boards, and printing plates. Photosensitive resin compositions capable of forming a positive image have been used which are of the type comprising an alkali-soluble novolak resin mixed with a quinone diazide compound. In such a system, the quinone diazide compound is soluble in an organic solvent only and not soluble in an aqueous solution of alkali, which characteristic is utilized in such a way that the compound is present within the system as a dissolution inhibitor against the developing solution which is an aqueous solution of alkali. When the compound is subjected to ultraviolet light irradiation, the quinone diazide group therein is decomposed to produce a carboxylic acid radical via ketene, which is soluble in the aqueous solution of alkali, and this facilitates development.
However, in such a system, the composition involves some brittleness when it is made into a resist film. Another problem is that the composition is not found very satisfactory in its contact behavior relative to the substrate. As such, there exists a need for improvement.
The present inventors already proposed a composition which is produced from a combination of a polyepoxide compound, a compound having a phenolic hydroxyl group, and a quinone diazidic acid halide, by causing all these substances to react with each other (U.S. Pat. No. 4,999,274). In such a system, the quinone diazidic photosensitive component itself has good film-forming properties, good flexibility, good adhesiveness relative to the substrate, and good solubility in alkali after exposure to light, and further it is highly compatible with an alkali-soluble resin.
The present inventors made an attempt at further improving the exposure sensitivity of the composition. As a result of their study, it was found that an improvement in the exposure sensitivity, that is, an improvement in the solubility of the composition after exposure to light could be achieved by controlling an addition rate of a naphthoquinone diazide acid halide, which is highly hydrophobic, to a low rate. In this case, however, the affinity of the unexposed area or printing area for the developing solution is increased, so that the function of the positive-type photosensitive material as a dissolution inhibitor is lost, which fact is likely to lead to the trouble of swelling or partial dissolution during the stage of development. This tells that exposure sensitivity improvement and resistance to swelling or dissolution are factors incompatible with each other.